Reciprocating piston type compressors typically employ suction and discharge pressure actuated valving mounted at the end of the cylinder housing. When designing these valve assemblies, it is of critical importance to overall system operation to provide a sufficiently large port area to permit the flow of a maximum amount of fluid within a given time period and at an acceptably small pressure drop. This is particularly true for refrigeration compressors employed in air conditioning systems because of the relatively high mass flow rates generally required in such systems.
Associated and conflicting with the desirability to maximize port area of a given size cylinder is the need to reduce the weight of the moving valve member. The reduction of the weight of the moving valve member will lead to a limitation of the inertial effect of the valve and a minimization of the noise level associated with the opening and closing of the valve.
Another important design objective is to minimize the re-expansion or clearance volume of the cylinder. The valving system and the cylinder top end wall should have a shape which is complimentary with the shape of the piston to enable the piston to reduce the volume of the compression chamber to a minimum when the piston is at top dead center of its stroke without restricting gas flow. While it may be possible to accomplish this objective by designing a complex piston head shape, manufacturing of this complex shape becomes excessively expensive, the assembly becomes more difficult and throttling losses generally occur as the piston approaches top dead center. Reduction of the re-expansion volume is of great importance in refrigeration compressors having relatively low mass flow rates, such as those units employed in very low temperature refrigeration systems, as well as in compressors used in heat pump applications.
A typical prior art valve assembly which has been developed to meet the above defined design criteria and solve some of the problems associated with the design of valve assemblies is shown in Applicants' Assignee's U.S. Letters Patent No. 4,877,382.
The valve assemblies disclosed in the aforesaid Letters patent No. 4,877,382 and particularly the suction valve insert in the form of an annular ring have performed satisfactorily in prior art compressor assemblies. These prior art compressor assemblies used a chlorofluorocarbon (CFC) refrigerant or a hydrochlorofluorocarbon (HCFC) refrigerant. The lubricating oil for these CFC and HCFC compressors has been a mineral oil based lubricant. The combination of the CFC or HCFC refrigerant and the mineral oil based lubricant provides sufficient cooling and lubrication for the insert in these prior art compressors. CFC and HCFC refrigerants are being phased out in refrigerant compressors due to the well known problems associated with the ozone layer. One refrigerant which is being utilized to replace the CFC and HCFC refrigerant is a hydrofluorocarbon (HFC) refrigerant.
HFC refrigerants do not have an adverse affect on the ozone layer and they are quickly becoming the choice of refrigerant to replace the CFC and HCFC refrigerants. When using HFC refrigerants, the mineral oil based lubricants lose some of their effectiveness and they need to be replaced with alternate and more effective lubricating oils. One lubricant which has shown to be compatible with and effective with HFC refrigerants is a polyolester based lubricant. While the polyolester based lubricants have proven to be a suitable replacement for the mineral oil based lubricants when using HFC refrigerants, there has always been the need to improve and extend the durability of the reciprocating piston designs of compressors.
One component which is being continuously improved is the reed valves associated with the discharge and suction valves of the compressor. The present invention provides the art with a reed valve having a laser hardened retention tab which significantly improves the durability of the reed valve.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.